Semiconductor image sensors are used for sensing light. Complementary metal-oxide-semiconductor (CMOS) image sensors and charge-coupled device (CCD) sensors are widely used in a variety of applications, including, e.g., webcams, digital video cameras, digital single-lens reflex (SLR) cameras, digital mirrorless cameras, digital mobile phone cameras, and/or the like. Such devices use an array of sensor picture elements (pixels) employing, e.g., photodiodes to absorb electromagnetic radiation and convert the absorbed radiation into electrical signals (photocurrent). A backside illuminated (BSI) image sensor is one such device.
With shrinking device feature size, conventional BSI image sensors may suffer from problems involving crosstalk (XT) and blooming. One form of XT occurs when a photon falling on a sensor pixel is falsely detected by a neighboring pixel. Blooming occurs when the electrical charge in a given sensor pixel exceeds a peak saturation level and leaks over to adjacent pixels. These problems may be caused or aggravated by poor isolation between adjacent pixels in an image sensor array.
Corresponding numerals and symbols in the different figures generally refer to corresponding elements, unless otherwise indicated. The figures are drawn to representatively illustrate relevant aspects of disclosed embodiments and are not necessarily drawn to scale.